While Google’s Android operating system has a lead over iOS in overall market share, it faces a hard barrier that blocks its ability to expand its lead much further: The loyalty of iOS users. AllThingsD points us to a new survey from the Yankee Group showing that 91% of iPhone users plan to buy an iPhone for the next smartphone while just 76% of Android users plan to stick with Android. Granted, this means that the majority of Android users are loyal to their platform but not to the same extent as Apple fans are loyal to the iPhone. Going forward, the Yankee Group thinks that the iPhone will expand its share of the mobile market and overtake Android, although it doesn’t think Android’s current market share will significantly deteriorate. Rather, most of the gains for iOS will come at the expense of non-smartphone operating systems that are slowly phased out over the next few years.